1. Field of the Invention
The invention relates to a method for tying additional function modules into a control facility of a switching system and to a switching system.
2. Description of the Related Art
The invention is based on the known principle governing the design of the control for a switching system. A good representation of such a design can, for example, be found in the article "Hardware and software of the service switching system PAsst" published in the journal PKI Technische Mitteilungen, 2/1989, pages 15-23, by Joachim Friedrichs et al.
This switching system includes a central processor which in, conjunction with peripheral processors, executes all check, management and control functions and constitutes the hardware platform for the software of the switching system.
The software of the switching system is based on a real time operating system and controls the entire routing flows, manages the system and checks the availability of all control components. In order to facilitate changes and updates in the software, the software is partitioned into function modules, also called building blocks, which constitute the constructive basic unit. Such a function module comprises programs and data and provides services to and accepts services from other function modules via a defined interface. The entire software is structured in form of several layers, each layer comprising one or more function modules. The layers are arranged in such a way that each function module can only use the services of the layers underneath. Hereby, the relationships between function modules are, in addition, systematically structured, thereby further simplifying changes in the software.
Although this principle for software architecture simplifies tying new function modules and changing existing function modules, such changes still carry the risk of malfunctioning and require a detailed understanding of the entire switching system.